The art of shoemaking has progressed from each individual shoe being built up on a shoe last to the stage where the shoe may be formed of man-made materials, such as plastics, and built up through one or more injection molding cycles. Styling changes, with the continued introduction of new molding materials, have caused the shoemaking industry to be faced with new and different requirements in shoe construction and injection molding apparatus for manufacturing same. These new and different requirements present a particular challenge to the shoemaking industry as they must continue to monitor and reduce production costs. That is, the shoemaking industry must diligently seek to achieve high production rates with low cost manufacturing techniques.
High production rates, as for example in the injection molding of a unitary sole and heel tread member, have been hampered by the slowness in which the molded article is released from the mold clearing such mold for reuse. Typically, the tread configuration of the unitary sole is ribbed such that there is considerable surface contact between the tread and the adjoining mold member. As a consequence, the unitary sole and heel tread member adheres tightly to the adjoining mold member. Valuable production time is lost in freeing the tread member from the mold member.
The recognition of this problem with lost production time is not new. A common non-mechanical method widely used in the shoe industry is called peeling or pulling out the unit sold by hand. Pliers or a similar device is used to grip the molded unit sole. This is time consuming and can result in damage to the molded article. Mechanical means have now been introduced by the industry in an attempt to reduce production time. An injector device for injection molding apparatus is taught, for example, in U.S. Pat. No. 3,914,086 to Hujik. Such patent teaches an ejector device which comprises a plurality of fingers slidably mounted in and forming a part of one mold member. Pressure means are provided for thrusting said fingers against the molded article to eject such article from said mold member. Other mechanical systems use air under pressure or a stripper plate to assist to removing the molded unit sole from the mold.
One significant disadvantage of such ejector systems is the cost of incorporating such systems into the mold member. Further, there are maintenance and possible replacement costs due to the use of movable parts. Production time and cost increases as a result of the operation and care of the pressure or activitating means thereof.
The present invention does not suffer from these disadvantages. The ejector device of this invention is simple, efficient, and requires no moving parts. Such device may be installed quickly in new or existing injection molding apparatus with little difficulty. All of the novel features of this invention will become apparent from the description to follow.